1. Field of the Invention
The present invention relates to an actuator for moving heads in a disk unit. More particularly, the present invention relates to the structure of an actuator having mounted thereon a control circuit for processing head signals to be exchanged with heads.
2. Description of the Related Art
In recent years, the trend of disk units including a magnetic disk unit has been towards compact and thin units in terms of shape and large units in terms of storage capacity. This leads to smaller heads and a lower signal level. A countermeasure against noise has been needed. Moreover, a lower cost is demanded.
Since the signal level for heads has decreased because of the smaller shape of the heads, it is necessary, for ensuring reliability of the heads against noise, to arrange a head integrated circuit (IC) for changing heads for reading and writing or amplifying read signals, a servo IC for amplifying read servo signals (the servo IC is included only when head positioning is performed by servo-surface servo, and replaced with the head IC when the positioning is performed by data-surface servo), and peripheral chips (parts) containing resistors, capacitors, and the like necessary for the ICs in the vicinity of the heads.
The head IC, servo IC, and peripheral chips are therefore mounted on an FPC (main FPC) sheet on the actuator located in the vicinity of the heads (refer to, for example, Japanese Unexamined Patent Publication No. 2-177075).
However, since a mounting area on the actuator is limited, part of the peripheral chips cannot, at present, be mounted on the main FPC sheet on the actuator, though an anti-noise characteristic is deteriorated. For solving this problem, the main FPC sheet is folded on the actuator in order to increase the mounting area.
For realizing a compact and thin disk unit, as already known, signal transfer among the heads, head IC, and servo IC is not achieved over leads (wires) but achieved via FPC sheets (relay FPC sheets).
In the structure in which the main FPC sheet is folded in order to expand the mounting area, a member for retaining the main FPC sheet in the folded state is needed, assembling work becomes more time-consuming, and manufacturing cost increases. Besides, there are problems that the anti-noise characteristic deteriorates with extension of signal transmission paths and that the increase in thickness of the main FPC sheet contradicts the trend toward a compact and thin shape.
With the employment of the relay FPC sheets, the portion of a disk unit in which the relay FPC sheet is employed can be made thinner. However, an area occupied by bonding lands is so large that a mounting area required for the head IC, servo IC, peripheral chips, and the like gets narrower. Thus, the known structure makes the problems more serious.